Use of the World Wide Web continues to increase, as does the amount and variety of content that is available to its users. Users of the World Wide Web commonly use browsers (web browsers) implemented on a web-enabled computing device to access content. Such devices include personal computers, laptop computers, netbook computers, smartphones and cell phones, among a number of other possible devices. Such web browsers are configured to read programmatic code and render that code as web pages, which may include rendering both audio and visual content contained in various media files (e.g., image, video and audio files), as well as performing other functions defined in the programmatic code. Web pages are generally implemented using programming languages such as HTML (including HTML5), CSS and JavaScript, among a number of other available programming languages.
Some browsers allow users to install add-ons (or extensions) to the browser, where such extensions add functionality to the browser and operate as an integrated part of the browser. For instance, an extension may provide a user access to its additional functionality by modifying a user-interface (UI) of the browser. As an example, a weather forecast extension may be added to a browser, where the extension provides easy access to weather information by adding an icon or a button to the UI of the browser. A user may then interact with the extension's button or icon (e.g., by clicking it or hovering over it with a pointing device) to obtain weather information, rather than having to browse to a weather related web page in order to obtain weather information.
Browser extensions are generally implemented using programmatic code that is written using the same programming languages that are used for implementing web pages, such as JavaScript. From a browser's perspective, extensions effectively function as web pages that are an integrated part of the browser once they are installed. By installing extensions that are of interest to him or her, a user can effectively create a custom browser that includes the functionality of the extensions they choose to install. For example, a user may utilize extensions to play synthesized text-to-speech, for example when reading a book via a web browser. It may be useful for extensions to exchange messages, while maintaining a user's privacy and while allowing a web browser to cleanly handle errors.